Deputy technology editor

Several Vodafone staff artificially inflated customer numbers to earn commissions as high as $5000 a month, say former staff – a revelation that is likely to result in another PR nightmare for the beleaguered telco.

Sales staff in a Brisbane call centre responsible for winning new business customers participated in a practice known as ''SIM stacking''.

It involved them adding extra SIM cards to an account, allowing them to falsely claim they had hit monthly targets and earn higher commissions.

Vodafone confirmed ''some'' staff participated in the practice but refused to say how many.

One former staff member said commissions for sales staff could top $5000 a month if they participated in the practice. Weekly retainers were about $700 for casuals, the source said.

Other former staff said most business plans allowed for a maximum number of SIM cards to be added to them without the customer being charged extra.

Some Vodafone sales staff took advantage of this to make a higher commission, they said.

The business being sold a Vodafone package - none the wiser to how the commission structure worked - would often accept the extra SIMs as it did not cost more, former staff said.

SIM stacking was identified in June as Vodafone undertook a review of its business and begun a restructure. Former staff said those suspected of being involved were put on paid leave while investigated.

It is understood the telco has changed the commission structure so that it is based on a contract's total value in a bid to eradicate the problem.

The Brisbane unit involved was coincidentally shut down in June as Vodafone restructured its business.

It is understood senior management found evidence of SIM stacking during the restructure and called police, but no charges were laid.

Vodafone said it had investigated allegations of misconduct by some employees that involved allegations of SIM stacking.

It did not say how many staff were involved, but said it had ''taken swift and decisive action to address misconduct''.

"Vodafone will not tolerate any illegal or unethical behaviour by any of its employees," it said.